Riqueza y distribución de las diatomeas epilíticas indicadoras de contaminación en el río Angulo afluente del río Lerma, Méxic

Abstract

Background. The Angulo River has been subject to environmental deterioration as a result of agriculture practices and industrial discharges to its tributary. Goal. Determine the species of diatoms that indicate contamination and their distribution in the Angulo river, a tributary of the Lerma river. Methods. Twelve sites including 2 springs were selected during the low-water and post-rain periods of 2005. The samples were obtained by scraping the rocks to separate the attached diatoms. These were cleaned by oxidizing the sample with hydrochloric acid and hydrogen peroxide; permanent preparations were made with Naphrax® resin, for review with light microscopy. Results. 50 taxa belonging to 20 genera were identified, of which 5 species belong to central forms and 45 to pennate species. The taxa present in both periods were Achnanthidium minutissimum, Amphora pediculus, Luticola geoppertiana, Nitzschia amphibia, Nitzschia dissipata var. dissi- pata, Pleurosira laevis, Staurosira pinnata and Ulnaria ulna. The temperature, pH, dissolved oxygen and total dissolved solids in the Angulo river presented spatial variations and with it the species records. Conclusions. Representative taxa of eutrophic and non-eutrophic environments were found throughout the tributary, such as Nitzschia palea and Amphora pediculus, respectively. This study has provided relevant information re- garding the presence and distribution of diatom species that can be used as bioindicators of environmental conditions. specific.